Not Application
In the paper-making industry, in textile production, and in numerous other industrial enterprises, it is often desirable to provide a chemical treatment to a roll of fabric or other work product as it is being conveyed by a standard conveyor or other means. In order to chemically treat the fabric in question, often a processing plant will include a spray or aerosol-driven liquid chemical product for application directly on the fabric or work product as it moves along a conveyor system. Typically, the aerosol spray devices/nozzles are permanently mounted above or about the conveyor and the liquid is applied to the fabric as it moves along the conveyor system. The amount of chemical applied generally varies as a function of the velocity of the conveyor, the flow rate of the spray release and the transfer efficiency of the spray system.
As chemicals are applied to the conveyed work product, a frequent and persistent problem is the overspray of chemical waste produced by the system. In order to guarantee a thorough application of the chemical upon the work product, the spray nozzles typically output more chemical than is needed for the surface since the transfer efficiency is usually much less than one hundred percent. Accordingly, the excess chemical collects on the conveying equipment or factory floor below, or is exhausted with the air effluent creating numerous problems including disposal costs, housekeeping, and the cost of the wasted chemicals themselves. Depending on the properties of the chemical, there may also be attendant environmental hazards including degradation of the equipment and personnel safety concerns. For these reasons, it is important to minimize the amount of overspray and minimize the escape of overspray.
In many chemical applications, the overspray from the applied chemical can take the form of a vapor mist with finer dispersed droplets than typical sprayed liquids. In these situations, not only does overspray result in wasted chemical product below and about the processing equipment, but airborne overspray can also travel to surrounding equipment and facilities. In these situations, it is even more important to have an adequate means for collecting and disposing of chemical overspray.
Industrial plants have been wrestling with the problems described above for decades. Accordingly, the prior art is replete with many varieties of overspray collection systems and air/liquid separators for accomplishing this purpose, as well as a wide assortment of collection basins and other forms of dealing with chemical overspray. Generally speaking, the prior art systems are marginal depending upon the task called upon to perform, and some of the prior art devices create challenges or hazards of their own.
The prior art features a wide assortment of air filters and air/chemical separation devices that have been developed over the years. Many of the prior art devices are essentially fibrous filters which are used to trap solid particulates and/or liquid solvent for separation from a gas stream. For a finely atomized mist, such devices are not adequate.
U.S. Pat. No. 1,772,037 to Bradshaw features a plurality of centrifugal separators. The Bradshaw device applies a centrifugal force on a flowing moisture stream to separate liquid from a current of gas against a plurality of baffles. The baffles increase in curvature as the inner or outer ends are approached to enhance the centrifugal effect. Likewise, U.S. Pat. No. 3,977,714 to McIlvaine features a gas separation device in which contaminant particles are entrapped in liquid droplets which are then spun to form a film on a surface of a plate. The contaminants are then discharged.
U.S. Pat. No. 4,061,478 to Hartwick discloses a self cleaning smoke filter. The filter includes a channel with multiple longitudinal sides angularly disposed, an inlet port for receiving gaseous emissions and an outlet port. The filter also contains a spraying means for producing a cleansing spray inside the channel.
U.S. Pat. No. 4,239,513 to Paul features a device for separating foreign particulates from a gas flow. The device uses wall plates to deflect the gas flow, subjecting the flow to a centrifugal force such that the foreign particulates are collected on the wall plates. The device contains spirally curved laminae to define passageways. Nozzles are arranged to feed moisture into the fluid flow to assist wet separation. While somewhat analogous to the present invention, the Paul device relies on the introduction of a water stream and a reversal of flow to form a secondary vortex to pull a film of fluid back into air suspension to mix with the solids and again be deposited on the wall plates as gas travels through the exit passages. Such a system is far more complicated and prone to error than the present system.
U.S. Pat. No. 5,906,676 to Drummond is an ejector-augmented overspray reclaim system. Drummond is directed to separating and reclaiming oversprayed powder from a powder coating spray system. In accordance with Drummond, the overspray collection system includes a trough located under a conveyor belt and an inlet passageway in fluid communication with the interior of the spray booth. A collection subsystem creates sub-ambient air flow in the inlet passageway. A rotating brush dislodges overspray articles from the conveyor. An airflow through a conduit is created by a rotating fan wheel in the collection subsystem, and the airflow is augmented by a compressed air injector that is disposed and oriented in the conduit such that it ejects compressed air in the direction of the inlet passageway. Accordingly, particulate matter settling in the trough becomes entrained in an airstream flowing into a collection subsystem. The collection subsystem includes a cyclone separator and a filter stack.
While the Drummond device is instructive, the present device features substantial innovations and improvements over Drummond. First of all, Drummond uses a rotating brush to move particulate matter to the bottom of the trough which is not necessary in the present invention. Furthermore, the use of an abrasive instrument would result in the tearing or at least scoring of a textile product, and hence, is not useful for many applications. In addition, Drummond features a compressed air injector for creating an air flow; such a subsystem is both unnecessary and counterproductive in the present device. The present device is dependant largely on a gradual or slow-velocity movement of the gas through the collection system. A compressed air injection system such as that featured in Drummond would introduce a turbulence that would frustrate the purposes of this invention.
The object of this invention is to provide an improved method and apparatus for the collection of a liquid from an overspray mist in a wide variety of manufacturing processes. Usage of this invention reduces the hazards and waste characterized by prior art methods, and provides a method and apparatus for the in-line recycling of applied liquids. In the preferred embodiment, the liquid overspray may be a chemical additive which is gas-entrained for direct application to a workpiece. The workpiece may be a paper product or a textile product, and will generally be in sheet form although other arrangements are possible. In order to achieve this objective, the present invention comprises a hooded recovery unit which is oriented above and about a conveyor system or other manufacturing line or process such that the liquid or chemical application upon the workpiece is achieved during a period in which the workpiece passes through the hooded recovery unit. The hooded recovery unit will hereafter be denoted and described as the xe2x80x9cspray application chamberxe2x80x9d. In this preferred embodiment, the process is a conveyor oriented such that it carries or secures the workpiece and passes through the spray application chamber. However, it is also possible that the process disclosed herein could be adapted to use in a stationary system in which the workpiece article(s) or sheet(s) is placed into the spray application chamber in batch-style processing.
In the preferred embodiment, a conveyor is arranged such as to orient the workpiece vertically through a processing chamber of a manufacturing process. Spray nozzles are oriented on one or both sides of the workpiece to direct a spray onto the workpiece from the side as it travels through the system. The conveyor system may also be arranged in any number of other manners including horizontal orientation of the workpiece. Furthermore, the conveyor system could be a standard belt or mesh-type conveyor, or it could be a cable or chain system with hooks or other means for attaching the workpiece to the conveyor.
As the workpiece passes through the recovery system, a gas-entrained liquid or chemical mist is applied to the workpiece, and the overspray invariably permeates the air within the walls of the spray application chamber. The ambient air in this vicinity may be heated by means of an electric resistance heater mounted in the chamber. A second chamber, a conditioning chamber, heats, cools, or otherwise processes ambient air to an appropriate temperature to suit the application, and an exhaust fan applies a low pressure vacuum to the conditioned air to move it into the surrounding walls of the spray application chamber. The conditioned air and liquid-permeated primary gas stream are moved by the same low pressure vacuum from the spray application chamber into a third chamber, a collection chamber which features a myriad of evase wicking baffles. The collection chamber of the recovery unit is also characterized by a reduction in the temperature of the conditioned air to approximate the dew point for the chemical or applied liquid. This area of the recovery unit is also characterized by specific air velocities and temperatures (which are dependent upon the nature of the liquid being removed) to maximize the efficiency of the evase wicking baffles.
The temperature in the overspray collection chamber is monitored electronically and adjusted accordingly to keep the conditioned air temperature within a few percentage points of the desired temperature. For waxy materials that are solid at room temperature, the chamber walls must stay above the melt point to maintain a flowable liquid for continuous recovery of reusable chemical. For finely atomized materials that are liquid at room temperature, the temperature of the chamber can be maintained at values to maximize droplet fall-out and coalescing in order to achieve maximum efficiency.
As the chemical mist travels through the overspray collection chamber, the chemical mist will settle and collect on said wicking baffles and the chemical will be gravity collected in one corner or other area of the chamber. Air velocity in the overspray collection chamber will be low with only enough pressure to keep the mist slightly moving. After separation of the liquid from the gas stream (usually air), the now clean air passes through a series of one or more conventional air filters to remove particulates such as paper dust, and is exhausted to the ambient factory floor or to the atmosphere.
A primary objective of the present invention is to provide a liquid recovery system that is both durable and flexible enough to be used in a wide assortment of chemical application systems. The device must also withstand physical and environmental challenges such as moisture, including acidic moisture, and around-the-clock usage.
Yet another objective of this invention is to create a liquid recovery system which is inexpensive to manufacture, inexpensive to install, and which increases the life-expectancy of the ancillary conveying equipment. In addition, a further objective of this invention is to create a liquid recovery unit that does not require frequent maintenance or replacement of component parts or dry filters. This invention achieves those objectives. Specifically, it is estimated that the apparatus disclosed in this invention would reasonably have a life-expectancy in excess of 25 years.
Another primary objective of the present invention is to provide an apparatus that is easy to transport into location in a variety of factory settings. Accordingly, this invention serves to reduce both the assembly cost and operations cost, saving valuable personnel resources.
Another primary objective of this invention is to provide a chemical recovery unit that does not itself create environmental hazards such as high heat, high velocity air flow, or noise concerns which would limit its applicability in some circumstances. The present device achieves these purposes entirely.
Another primary objective of the present invention is to provide an on-line, continuous recovery and recycle system for spray applied chemicals. Applicators will be able to recognize all the benefits of spray processes without suffering the direct and indirect costs of inherent spray inefficiencies.
As discussed above, the method and device of the present invention overcomes the disadvantages inherent in prior art methods and devices. In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangement of the components set forth in following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purposes of description and should not be regarded as limiting.
Accordingly, those skilled in the art will appreciate that the conception upon which this invention is based may readily be utilized as a basis for the design of other structures, methods, and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions in so far as they do not depart from the spirit of the present invention.
Furthermore, the purpose of the foregoing Abstract is to enable the U.S. Patent and Trademark Office and the public generally, and especially including the practitioners in the art who are not familiar with patent or legal terms or phraseology, to determine quickly from a cursory inspection, the nature and essence of the technical disclosure of the application. The Abstract is neither intended to define the invention of the application, nor is it intended to be limiting to the scope of the invention in any way.